1. Field of the Invention
This invention relates to an electronic flash device, and more particularly to a trigger circuit in the electronic flash device.
2. Description of the Prior Art
Conventional electronic flash devices known, for example, in U.S. Pat. Nos. 3,591,829 and 3,805,278 generally employ a trigger circuit of the type in which an electrical charge stored in a capacitor is caused to rapidly flow through the primary coil of a pulse transformer in response to the closure of a synchronous switch provided in a camera side or of a trigger switch of the electronic flash device, while a high-voltage pulse induced in the secondary coil of the transformer is applied to the trigger electrode of the flash tube and results in a discharge therethrough to emit a flash of light. With such a trigger circuit, a high voltage is directly applied from the electronic flash device to the synchronous switch of the camera, thereby giving a disadvantage of damaging the contacts of the synchronous switch by sparking or the like which may be encountered when the switch is opened or closed. Another disadvantage is that when a camera having an accessary shoe and synchronous terminals arranged in a common body is selected for use with a direct-connection type electronic flash device to make flash photography, a high voltage is applied from the electronic flash device to the synchro-terminals as well, so that if the operator accidentally puts his finger to the synchro-terminals, he will feel an electrical shock.